Stents are used to keep open body channels. For example, ureteral stents may provide drainage of urine from the kidneys to the bladder. Similarly, biliary stents may provide drainage of the bile ducts between the liver and gallbladder and between the gallbladder and small intestine. A stent is a flexible, tubular structure that is made from relatively inert materials (for example, silicon, teflon™, polyethylene, polyurethane, stainless steel, or nickel-titanium alloy). Often a stent may be perforated to provide small drainage holes along its length. Stents may also be shaped to define “hooks” at either end. For example, such hooks may prevent migration of a ureteral stent from the kidney toward the bladder or from the bladder upwards. A shortened ureteral stent has only one hook at the distal or kidney end of the stent. Often, shortened stents are used to reduce irritation caused by the presence of a stent within the lower ureter and within the bladder. With a shortened stent, the stent resides in the ureter, remote from the bladder and the ureteral orifice (i.e. the junction of the ureter and the bladder).
Indwelling stents periodically need to be removed or periodically replaced. Conventional stent removal procedures may be complex and may be painful, sometimes requiring general anesthesia.
A thin thread may be attached to a shortened stent to extend into the bladder to assist with the removal of the stent. However, such a shortened stent (with thread) requires endoscopic visualization of the threads so that they may be grasped, and the stent may be withdrawn. Although this is a relatively simple procedure, it requires specialized instruments used by an urologist in a sterile setting. Nevertheless, general anesthesia may also be required.
An alternative stent removal method is described in WO 99/58083, which employs the use of a tethered bead at the proximal or bladder end of the stent that may be removed with the aid of magnet tipped catheter.